Vasopressin is a nonapeptide hormone that is secreted primarily from the posterior pituitary gland. The hormone effects its actions through the vascular V-1 and renal V-2 receptor subtypes. The functions of vasopressin include contraction of uterine, bladder, and smooth muscle; stimulation of glycogen breakdown in the liver; induction of platelet aggregation; release of corticotropin from the anterior pituitary and stimulation of renal water reabsorption. As a neurotransmitter within the central nervous system (CNS), vasopressin can affect aggressive behavior, sexual behavior, the stress response, social behavior and memory. The V-1a receptor mediates central nervous system effects, contraction of smooth muscle and hepatic glycogenolytic effects of vasopressin, while the V-1b receptor mediates anterior pituitary effects of vasopressin. The V-2 receptor, presumably found only in the kidney, effects the antidiuretic actions of vasopressin via stimulation of adenylate cyclase.
Elevated plasma vasopressin levels appear to play a role in the pathogenesis of congestive heart failure (P. A. Van Zwieten, Progr. Pharmacol. Clin. Pharmacol. 1990, 7, 49). As progress toward the treatment of congestive heart failure, nonpeptide vasopressin V-2 receptor antagonists have induced low osmolality aquaresis and decreased peripheral resistance in conscious dogs with congestive heart failure (H. Ogawa, J. Med. Chem. 1996, 39, 3547). In certain pathological states, plasma vasopressin levels may be inappropriately elevated for a given osmolality, thereby resulting in renal water retention and hyponatremia. Hyponatremia, associated with edematous conditions (cirrhosis, congestive heart failure, renal failure), can be accompanied by the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Treatment of SIADH-compromised rats with a vasopressin V-2 antagonist has corrected their existing hyponatremia (G. Fujisawa, Kidney Int. 1993, 44(1), 19). Due in part to the contractile actions of vasopressin at its V-1 receptor in the vasculature, vasopressin V-1 antagonists have reduced blood pressure as a potential treatment for hypertension as well. Thus, vasopressin receptor antagonists are useful as therapeutics in the conditions of hypertension, congestive heart failure/cardiac insufficiency, coronary vasospasm, cardiac ischemia, liver cirrhosis, renal vasospasm, renal failure, cerebral edema and ischemia, stroke, thrombosis, and water retention.